¼ tsp. salt (I used salted butter so I cut back the salt, if
you use unsalted butter you can increase the salt to ¾ tsp.)

1/3 cup sour cream

For the crumb topping,

1 cup flour

¼ cup packed brown sugar

¼ tsp. ground cinnamon

4 tbsp. butter, melted

In a large bowl toss the chopped rhubarb with the sugar and
lemon juice. Set aside.

In a bowl beat the butter with the sugar and lemon zest
until light and fluffy.Add in the eggs
one at a time until well incorporated.Whisk
the flour, baking powder and salt together. Add ½ the flour mixture to the
batter and stir to just combine. Add half the sour cream and stir to combine, and
then repeat with the remaining flour mixture, ending with the last of the sour
cream.

Spray a 9x13 inch baking dish well with nonstick spray.Spread the batter in an even layer over the
bottom of the pan.

Spread the rhubarb over the batter.

In a small bowl stir together the flour, brown sugar and
cinnamon.Pour in the melted butter over
the mixture and stir with a fork until it resembles coarse crumbs.

Sprinkle the topping all over the rhubarb layer.

Bake in a 350 degree oven for 45-50 minutes or until the
edges pull away and a toothpick comes out clean.

Let the cake cool completely in the pan.

Cut the cake into small squares and serve as is or if you
are like me cut yourself a very large slice and top it with a big old scoop of
vanilla ice cream!